1. Field of the Invention
This invention relates to a solid-state image pickup device and a method for manufacturing the same. In particular, this invention relates to a solid-state image pickup device which makes it possible to uniformly maintain a distance between a wafer and a glass plate when the device is manufactured, and a method of manufacturing such a solid-state image pickup device.
2. Description of the Related Art
In recent years, digital cameras and video cameras utilizing a solid-state image pickup device such as a CCD or C-MOS element have been increasingly popularized and, at the same time, the techniques to further miniaturize the solid-state image pickup device by making use of a chip-size package (CSP) system have been developed. The solid-state image pickup device of such a small size is suitable in mounting it on electronic equipments such as mobile telephone where miniaturization, weight-saving and the reduction of thickness are desired.
This small scale solid-state image pickup device is constructed such that a solid-state image pickup chip having a large number of microlenses attached to the light-receiving surface thereof is disposed to face an infrared-cutting transparent glass plate with a spacer being interposed therebetween so as to uniformly maintain a predetermined distance between the chip and the glass plate, and that the peripheral gap portion between the chip and the glass plate is sealed with an adhesive (for example, JP-A 2002-329852).
The small scale solid-state image pickup device constructed in this manner can be manufactured by a method wherein a wafer having a plurality of the solid-state image pickup chips fabricated in one surface portion thereof is adhered face to face to an infrared-cutting transparent glass plate with a frame-like spacer being interposed therebetween and then the rear surface of the wafer is polished to reduce the thickness to about 30 to 100 μm, after which the resultant laminated body is cut so as to separate the solid-state image pickup chips individually, thus manufacturing the small scale solid-state image pickup device.
In this case, although the distance between the wafer and the infrared-cutting transparent glass plate is regulated by the height of the spacer, this distance is required to be uniform throughout the entire surface of the wafer having a diameter of 20-30 cm. However, the conventional spacer is accompanied with a problem that when pressure is applied to the infrared-cutting transparent glass plate on the occasion of laminating the glass plate to the wafer, the spacer is easily compressed so that it is impossible to uniformly maintain the distance between the wafer and glass plate throughout the entire surface of the wafer.
On the other hand, in the case of the conventional spacer, when pressure is applied to the infrared-cutting transparent glass plate on the occasion of laminating the glass plate to the wafer, bubbles may be entrapped on the inner side of the frame-like spacer, since this frame-like spacer is not provided with any kind outlet through which the gas existing inside the frame-like spacer is enabled to escape. Due to the pressure of this entrapped gas, an adhesive may be squeezed out of this assembled body, thus giving rise to the generation of defectives.